(1) Field of the Invention
The present invention relates to a vehicle behavior judgment system and a vehicle occupant-protecting system using such a vehicle behavior judgment system. More particularly, the invention relates to improved rollover judgment based on at least the rolling angular velocity.
(2) Related Art Statement
There is known an occupant-protecting system which is adapted to protect an occupant from impact caused by rollover of a vehicle through operating an occupant-protecting device including an airbag system commencing with a curtain airbag, a seat belt pretensioner device and the like when the vehicle rolls over. See JP-A 2002-200962. As discussed in JP-A 2002-200962, the terms “rollover” and “roll over” used throughout herein include “turnover”, “trip over”, “flip over”, “bounce over”, “fall over”, etc.
The occupant-protecting system for the vehicle judges whether the vehicle rolls over or not, based on two-dimensional values defined by a rolling angle and a rolling angular velocity (rolling rate), and controls the operation of the occupant-protecting device based on this judgment result as to “rollover”.
In the technique of JP-A 2002-200962, the rolling angular velocity ω is mainly detected by a rolling angular velocity sensor (rolling angular velocity detector). The sensor may output a signal in which a noise component N is superposed upon a normal signal S representing an actual rolling angular velocity ω, when the sensor receives influences of high-frequency noise generated from a variety of devices such as an ignition plug of an engine mounted on the vehicle. The rolling angular velocity containing such a noise component N exhibits a value instantaneously projecting.
If whether rollover occurred or not is judged based on such an instantaneously projecting value, an erroneous judgment result may be generated, although the vehicle is actually not in a state resulting in rollover.